Oscillation detector and rectifier.



G. W. PIGKARD. oaomumn nm'no'ron AND nncmnzn. APPLIOATIQK FILED SEPT. B, 1907.

' Patented Feb. 16,1909.

J X 1 a 6 w 1 Inventor;

Zyte t:

action. When used-Without electroplating;

the apparent resistance is over a megohrn for a currentfot a few tenths of a microamperelwhile for a current. .of 300, -.rnic'roamperes the "apparent reslstanoeis as low' as f Fig. 1 the insulating base .Bhas ax super-baseC of conducting material, asz'cop-- per, secured to, it by a screw S, As stated above the :plating is not necessary, this being'because the support for there'otifying conductor will naturally have 'a contact with it of larger area (thereby becoming the j neutral or meiiective contact); than the effective small contact between the rect fymg conductor' and itscooperating. electrode. Thus-ion: exam 1e,fno plating is shown in Fig. 2. '-The usible. metal of Fig. 3 is the electrical equivalent of the lating P ."of Fig. 1, each having for its,-

unction to .insure the continued existence of such conditions-as will not tend to oppose the useful action at the etiectlve contact,

.which .is the small-aread contact .with: elec trode D. The coating P or fusible-metal M may be replaced by any other equivalent (providedt at the rectifying conductor has its effective small "good contact with its cooperating electrode D, as by a conducting ads of the crystnLshown) whicir rnay be sue as tojnsure the continued existence at the other circuitc'ontact, with the rectifying conductor, (irrespective of accidental changes in adjustments,-or of breakage of the rectifying conductoflf of such largeraread contact than that with the cooperating electrode D, as will not tend to substantially oppose the useful action at the" smaller contact.

Theprystal .(shown in edge view at X in Fig,

2) has its lower edge elctro-piated as with copper,- at P, which restson the super-base The base B carries a conducting standard E, screw-threaded to -receivc the deli cately-threaded adjusting contact-screw D,

a portion of the lower end of which makes. the effective" edge contact with the-edge or minute conducting portion of the crystal X. In Fig. 2 the lower edge {of the crystal -X engages directlyWithsuper-base '0 without individual crystal of silicid 0 any plating; and-in Fig. 3 the su er-base C is cu shaped and contains fusib e. metal M in w 'ch the crystal X is supported. This carbon, when used as specified, has every marked rectifying effect; upbn alternating electromotive forces, as. discovered in the course of my in vestigations and obsen'ations. Also, the

, change in conductivity as the potential acrossthe edge-contact terminals of the dividual crystal is varied, is 'characterlstw, as the curve ofcconductance (for the particularicrystal used in some of my tests) has a criticalportion between one volt and one and onetenth volts, Wherean increase often per cent.in the GlBCtIOlTlGtlV force causes a erati've as a'wireless I telegraph detectorwit out;a local gsource 0f electromotlve force, I devised a clrcuit arrangement for the or tel dum tested by-me.

charige in the conductanceof more than 100.

r cent. For this re'a'son, although the rec iallymg acitionofthe individual crystal is op- 1- po'ssessing said, -peculiar property, whic in eluded not only-a local battery, (A, Fi 4) but also a'p'otentiometer It, (with com ucting rod 1 and slide 2),in' order to quite ac- .curatel control the voltage in the local cir euit W on the crystal is used as a wireless telegraphydetector, in order that the crystal maybe-operated on the steepest part of the conductance-curve, andtherefore with mnximum ,cfiicrency. I find that in practice a battery and an adjustrnent. of the potentiometer which reduces a difference .of o'- tential acrosst e terminals of the crysta of between one volt and three volts, depending of.course upon the characteristics of the particul'ar-cryst'al used, produces the best re sults;

In Ti 5 is shown a conductance curve of particular crystal of 'carborundum us'ed i1. 2

impaired. The sha e of the curve, however,

is characteristic of'a l specimens'oi carborun- With the particular rectifying conductor herein disclosed, the positive (carbon or copper) pole of the battery (indicated as 'usual by the longer vertical line, at the left,

Fig. 4) is connected to' the cooperatin conducting memb'er D, inorder to apply tlie low auxiliar electromotive force, so as to cause an auxi iary current to flow into the rectitying conductor X in a direction from its effective contact with the cooperating member D, which isthe same direction as. that of the currents [rectified by the conductor X when the latter is of carborunduni. This connection-shown in the drawing insures the optimuin working of the rectifyin conductor with respectto its optimum conductance in combination with the'requisite value of aux-' iliarj source of direct electromotive force,

that is to say, insures operation of the. rectifier at the stee est part. of its curve of conductance for e rectified current. When used as a detector, and with a local source of,

electromotive force provided with means to control the same within the liinits 0f the contact at the best-conducting exterior porsteepest part oi the conductance curve of the crystal, the individual crystal device .seems to o we its efliciency not only to the high positive coefficient of conductiiity of thematerial useful under the influence of heat-omlsed l y the oscillations,- but also to the, comparative smallness of the effective edge contact which limits the actionto and concentrates it at every small volume of the crystal, while providing a goodand efiective tion of the crystal. In a commercially sensr tive'dete'ctor thebporstive portion of the crystal is n ittle'pyramidal mass, a thoumaterial; The area of edge contact with the electrode is also extreme-iv small; being of the order of a few millionthsof a square; 20

inch. This of course refers to effective electrical contact, ond not physical contact, which may bo-meny times lar er. .course,. various forins of mechanical holders may be eii'iployed with the invention.

When-used as a rectifier oi'oscillations of lower frequenc than those commonly used in wirelessteofraphy, the .action of the some individual. crystal device, with the edge contacts, or conducting edge contacts as y metal-plating the neutral contact, is more olficient, particular-1 with the very low frequency currents o the general art. The action of the same device is possible however as a. rectifying detector ohwireless telegraphy. oscillations, without a battery, but this errengement is not as eflicient commercially as with the battery .and o*cntiometer, end not-so readily contm loble, unless cr. stals be used of other substances than our orundum and possessing the same groperty in greater degree, and which may e obtained by 'nrl-Jitrnry trial ofvarious.

substances or By their known and tabuhated or measurable properties.

It is not {ct established as tor'lmt property of t e clysml contributes to its rectifying effect, or whether or not heat enters into this or in precisely what way the auxilinr cectroniotive force aids the rectify e ect, except that at a particular potential, herein specified for one rectifying conductor such RS czirl-iorundum, ilu-rc is n correspon ing steepest portion of the conductcncc curve, irhich is. the particular conductoiynt which portion the rectifying .efliciency of such conductor is, greatly enhanced; that is to say, the rectifyingconduclur is opcrqte l st llinsteepest part ol ltscurw of clin l ietniicel'ur the rec-tilled current. l'ho fact remains, however, as l have tllf t'ufl!lfiltl, that the device is an efficient rcctilicig-on gcctifyn g tector as well as :1. conl rolling dctccloriur it local battery circuit.

fii The device herein described, consisting sandth ofan inch or so on aned 'e and contaming about a'b-illionth ofeciibic inch of- Oi. having the rectifying property chnlucteristic of good contact at its edges or at least one trodes, is much more sensitive and reliable est art'of the conductance curve, which. is muc inoro .cliicicnt than the rectifying. efl'cct alone, in the case of crystnlsnot in a higher degree than silicide of carbon. The no of an individual crystal, ilh cdge contacts or \iith at least uneiiectivc contact uith one edge, in suchn controlled circuit, provides a device which is commercially operative. .In brief, the invention concerns. irrcspccliire at least one cryst-sl edge, which (hi-rob mnstitutos the cfloctivc and useful tnnluvl.

In rectification, the individual crystal is useful in that'it. provides limited ('umliu'i-irity and small area of contactpoints. 'Elucrystal has clear-l1. defined cilgvs, and Sumo crystals have limited conductiritr nlmuz planes. In somecrises, us in that ol siliciilc of carbon, or cnrborundum, thcsurfsces of the crystal are of higher resist-once than the edges, whichperniits' the making of very small creed contacts. Laminar conductivit; may exist in some crystals, which yet further constricts the current path.

The pressure by the screw 1) (Fig. 1) will .vary in accordance with the particular crystel of which X is cmnposed. lmi in all cases will be such as to produce gum! comm-L. Thebestcrystals are those which, in slidition to the other desired properties, will will stnnd high temperature without injury. Also the crystals should be stable in air, that is,as free as possible from oxidation; or else they should bflvltl-(ltl in oil or vacuum when in use, or otherwise. protected from |-\'i l:1 tiou.

-1. As an element of n means for ro -civic; iiitclligcnce communicated ll olrctrom hvtlc waves, on individual (undue-ling; crysltllo i h t '3. As on element of n menus iur receiving inlcllig; I e, cunmmniciiled by eil ectroumr,- netic \\'n i sin individual ciystial cl low colulm-tirit v, and having aconduciiizg body of on individual crystal held firmlv rind inedge, between two flat copper-faced elec-' in operation than a mass or body'of'crystals,"

of alleles, the individualilv of contact .x'itlr operation within narrow limits at the steepll l 3. Means .for'recoiving intelligence on1- nnnucntetl by electromagnetic waves, which comprises an individual conduct-in crystal and on elcctrot 0 having goodbut minute cont-act with the edge of the crystal. i

4. A, rectifier of alternating clcctromotivo forces, which com n'ises in individual conducting crystal of low conductivity.

5. A rectifying device for alternating electromotive Forces, which. eoniirises an individual conducting crystal of low conductiw ity and havin 6. Means or receiving intelligence coniinunic-nt-ed by electromagnetic \WLVGS, which comprises a conducting crystal having '12,

' high positive conductivity coeiiicient, a local source of electroinotive force, and menus for operating said crystal within the limits of the steepestpart of the conductance curve. of the crystal.

7. Menus for rectifying alterm ting electroinotivc forces, which comprises an inclividual conducting crystal having a metallicdeposition upon its edge.

8. Means for rectifying the alto-mating elcctrom0ti\-o fOlP-ur; of electri al oscillations in wireless telegraph which comprises on individual conducting crystal. and en electrode in good contact with the edge of the crystal.

9. Means for ICL'GlYlllg intelligence communicn'teil by electrcmagneiic waves, which comprises u. concluciiiu crystal having a high positive-coefficient of conductivity. and a ocnl source of olcctromotive for-cc lhi-reior of suitable l'OpOlilUnSiiiOPiF" i an m; in within the units of tom a e! our: 0i 1io'omluct-nnec cur-w.

1:]. As 0. menus f r rec-oi comuninicatcd by electromagnetic waves, the comhinatiim with ducting crystal oi we; liiglrpusith'c cm-iiii-icui conducting edgrs; o," no rim-Erode having a minute good contnrr with the ruminating edge of the imlividual crystal: 3. local source of clcctroiuotivc Port-o cramim! ioenid electrode and mental; and lilfiilll: for limiting the eleciromotirc force of said locgil SOHICC bctween one volt alncl three volts.

1 A rcctil' 'ng novice for alternating electromotivc orees,- which coin rises a. conelectromotive forces, which comprises a. cona metallic deposit-ion upon it.

a conducting ring intelligent-o F :in individual con-i i i l l l l l extremely low conducminty and possessing the proper-t of rectification,- iucomb'inat-ron wit-hen e act-rode of conducting material in good electric-at coutact with c good-conductin p'ortionofraicl rectifying concluctor, Stilt contact being effectively minute; and .nicans for applying a direct electmmotirc force across suiil rectifyim conductor to o crate it sul'isini'itinlly within the limits of it ie slccpcstpurl of ducting solid having its curve of conductance for the rectified,

current.

13. In an apparatus for ing electro'motive forces, useful, for cmmple, in receiving intelligence communicated by electromagnetic waves, the com binction with solid having extremely low couiluctivity and possessing the propertv 0f rectification, of means for applying a directclectromot-ivo force across said conductor to operate it substantially Within the limits of the steepest part of its conductance curve. 14. A wireless telegraph detector, which comprises a rectifying conducting crystal, at cooperating conductor operetiveh in srnalhnreaclelectrical contact with'a. conducting surface of said rectifyim crystal, and means for applying across saii' conductors an elcctroinotn'c force of a critical value for operating said rectifying conductor suhstautially within the limits of the steepest portion of its (-oiuluctance curve.

i5. A wireless tclcgrnph detector which comprises a rectifying coi'ulucting crystal of i-nrboruntlum. a cooperating conductor opi-rniiri-ly in smnil-nrcnd electrical contact niih' a conducting edge of said carbormzdum crystal, and means for applying across said conductors nu electrouuptivc force ol :1 critical vnluezfor operating sold rectifying conductor s'nhstnntiall; within the limitsof the steepest portion of its condncta-nce curve.

16. A rectifying apparatus for alternating and oscillating electromutivc forces, which comprises a conduct ing substance possess ng the import of rectification; a coopcratiu corn uctor having an operative Silllllldtl'ttlil contact with acondueting surface of said rectifying substance; and means for nppiying across said cooperating conductors n a definite direction withrespect to their operative contact, '2; direct electromct ve force oficheracteristic Volta? for operating said-rectifying conductor wit in the steepest part of its conductance curve.

G ll llllh' LHARWHITUER' i'ICliA it D.

rectifying alternat- 

